The invention is addressed to the resolution of water-bituminous emulsions which are stabilized with clay by treatment with resins. The invention is further concerned with an apparatus for the separation of water from bitumen which has been produced, or brought to the earth's surface from a substrate, in the form of an oil-in-water emulsion by an in-situ recovery process.
The emulsion which usually results from a tar sand recovery process is normally very tight. It comes from the ground stabilized by clays and consists of complexes of oil and water. Physically, the bitumen droplets are believed to be surrounded by a layer of water, which in turn is surrounded by clays. The latter in turn can be surrounded by a film of bitumen which is enclosed in a thin film of water. This type of emulsion is found to be difficult to break through the use of standard chemicals whereby the bitumen might be freed.
The API gravity of the bitumen normally falls within the range of approximately 7 to 9, i.e., being heavier than water. However, to prompt the desired separation from water by flotation, the solution is treated with certain diluents which function to increase the bitumen's API gravity or, stated otherwise, to lessen its specific gravity.
Toward breaking the solution, it has been found that diluents or attempts to mix diluents with the bitumen emulsion, usually result in the diluent floating to the surface of the emulsion. Even when chemicals are added to, and mixed with the emulsion along with a diluent agent as is normally practiced, the diluent will still float to the top.
It is noted, however, that after a due time period of of almost two to three hours at standard temperature, if the entire aqueous solution is again subjected to a mixing action the emulsion will tend to break, the water segment moving downward and the bitumen then separating and rising to the top of the water layer.
In summary, it is believed that a complete and thorough mixing of the chemicals with the bitumen emulsion is important. Further the reaction time required for the chemicals to act should be somewhat extended. This fact necessitates an overly long treatment time, often mandates the use of cumbersome apparatus, or both.
Numerous hot water extraction methods exist for separating crude oil from bituminous sand (tar sands, oil sands and the like). These methods involve mixing the sands with hot or cold water and separating sand from the resulting emulsions.
Previous methods used to break bitumen emulsions resulting from hot water extraction processes are known in the art and have been used with a degree of success. Among such other ways are those by the techniques described in U.S. Pat. No. 3,607,721.
My issued patent U.S. Pat. No. 4,302,362, dated Nov. 24, 1981, discloses and claims a process for breaking an oil-in-water emulsion which is received or produced from a tar sand formation. The process includes the feature of contacting emulsion with a polyethylene polymeric resin having a molecular weight in the range of 100,000 and 7,000,000.
This emulsion, as disclosed, is permitted to stand for a period of time up to several hours, with or without the addition of diluent materials. Thereafter, the emulsion will break, permitting the separate removal of the diluent, and the oil mixture which floats at the surface of the water.
A primary object of the present invention therefore is to provide a novel method and apparatus for breaking a bitumen emulsion. A further object is to provide an apparatus which is capable of resolving a bitumen emulsion into discrete elements of water and bitumen through the expedient of pretreating the emulsion prior to its being separated. A still further object is to provide a premixing apparatus which initially receives a bitumen emulsion, and thereafter causes it to achieve a more thorough intermixing with additives and diluents over a sufficient period of time to facilitate the subsequent breaking of the emulsion and separation of the bitumen content.
Toward achieving these objectives, the presently disclosed apparatus provides, in brief, a separator which embodies an enlarged chamber into which pretreated emulsion is fed. The emulsion is initially subjected to a knockout operation wherein a major part of the water is disposed of.
In the succeeding steps, the emulsion is subjected to a coalescing action. Here, the emulsion is caused to pass through a plurality of small openings or ports characterized by relatively sharp peripheral edges which scarify the individual emulsion particles by a shear action. This physically removes or peels off layers of clay and/or water, and thus frees the innermost bitumen core.
Raw emulsion, normally in heated condition, is provided from a supply which in turn is produced from a subterranean tar sand source. The emulsion pretreating apparatus comprises primarily a chamber into which basic emulsion is pumped after it has been initially intermixed with a predetermined amount of diluent and various chemicals. The latter, as noted, function to expedite the breaking process.
The emulsion can be produced from its tar sand in-situ substrate by any one of a number of known stimulating processes. It is thereafter circulated through an elongated, discontinuous flow path by way of a plurality of passages. The discharge end of the discontinuous flow path is communicated with the emulsion separator inlet to deliver the stream of premixed and circulated emulsion thereto.
The emulsion premixer includes a recirculating pump having its suction communicated with a source to receive a portion of the entire emulsion flow at a point toward the downstream end of the discontinuous flow path. The recirculating pump receives at least a part of the emulsion flow and causes it to intermix with the main emulsion stream entering the flow path .